Chalk Line Marking Device

1. Field

The field of the invention is carpenters' aid devices, and more particularly such devices for preparatory marking for installation of structural members.

2. State of the Art

In wood frame building construction, wall studs, joists, rafters and other components must often be installed at regularly spaced intervals along a straight line. The marking of a straight line between widely spaced points is typically done by using a chalk dust impregnated cord, stretched along a base member or the like providing a working surface between the points. The cord is snapped against the working surface, leaving a temporary straight line of chalk dust. Intervals along this line are then marked with pencil and carpenter's ruler, flexible tape or the like. However, in some instances, the chalk line cord has been modified to produce the spacing marks directly. U.S. Pat. No. 4,152,836 discloses a chalk line marker cord having a metal wire core covered by a flexible sleeve. The sleeve material is smooth and otherwise adapted to be resistant to retention of chalk dust. At intervals along the cord, the chalk resistant sleeve is discontinued for a short distance to be replaced by short segments of material adapted to retain the chalk. Use of this cord is intended to produce a line of correctly spaced marks along the working surface. The desired intervals are indicated by reference to the ends of the marks deposited upon the working surface. However, these marks tend to be less than precisely defined. The points of transition from chalk to bare surface tend to vary considerably. Extraneous marks also occur from chalk adhering in unwanted sites even along the smooth sleeve. Another troublesome factor is non-uniform chalking in the chalk retaining sections.

A British Patent No. 1,026,051 discloses an interval marking chalk line having chalk retention resistant sleeves, of gloss paint, e.g., at intervals. The marked line thus has spaced interruptions, rather than spaced marks as with the above discussed device. However, the same basic shortcomings exist. Any non-uniformity in the chalking of the sections leads to confusing markings by spurious interruptions of the line in the case of the British Patent, or by equally spurious extraneous marks with the U.S. patent.

Some of the above shortcomings tend to be countered by another device, disclosed in U.S. Pat. No. 4,679,325, albeit with increased complexity and cost. A flat tape, generally resistant to chalk, is used, which has perforations at the required intervals. A chalk impregnatable felt strip is provided on the side of the tape away from the working surface. The perforations allow the chalk to be deposited upon the working surfaces through these regularly spaced perforations. The tape may be less stretchable than the small wire cord with the other devices discussed herein. This contributes to accuracy in the location of the interval marks. Since the chalk carrying cloth is held away from actual contact with the working surface, the deposit of the chalk dust therethrough may be unreliable. The tape, as in the case of the wire sheath, does not completely reject deposits of chalk. With all these prior art devices, confusing unplanned marks may occur. All may produce imprecisely defined marks. Clearly, there is a need for a chalk interval marking device which avoids extraneous marks and reliably produces well defined interval marks. No prior art device provides for the contact of the working surface by only the portion of the line adapted to provide the marks to prevent the occurrence of extraneous marks.

With the foregoing in mind, the present invention eliminates or substantially alleviates the disadvantages in the prior art, by providing a chalk marking line assembly adapted to resist retention of chalk dust except upon the outermost edges of marking units attached at spaced intervals along the line. Each marking unit extends rigidly out perpendicularly to the line when it is tightened for use, holding it from contact with the working surface. This prevents transfer of any inadvertent clinging deposits of chalk dust to the working surface.

The chalk marking units each preferably comprise a pair of rigid washers of chalk resistant material, mounted at intervals along the line. Between each pair of rigid washers is sandwiched a thin washer of material such as felt, selected for its chalk holding properties. Advantageously, the rigid washers may each be mounted as flanges upon a thin metallic sleeve crimped onto the line in the desired location. The felt marking washers are impregnated with chalk in conventional fashion, preferably within a chalk dust containing canister. The canister has an internal chalk line storage spool with an externally operated crank. Advantageously, each flange may be provided with a tapered cowling, to prevent the chalk particles from being drawn from the canister along with the line. Or, each flange may incorporate a tapered transition for the same purpose.

It is therefore the principal object of the invention to provide an improved device for producing a series of chalk marks at preselected intervals along a line, while substantially preventing unwanted confusing additional chalk marks.

In the drawings, which represent the best modes presently contemplated for carrying out the invention,

FIG. 1 is a perspective drawing of a chalk line marking device in accordance with the invention, the cord assembly thereof being shown fragmentally, and the canister thereof being partially cut away, drawn to substantially full scale,

FIG. 2 a side elevation view of one of the chalk marking units of the invention, taken along line 2--2 of FIG. 1, drawn an enlarged scale,

FIG. 3 a vertical sectional view of the chalk marking unit of FIG. 2, drawn to the same scale,

FIG. 4 a vertical sectional view of a fragment of the chalk marking unit of FIG. 3, drawn to an enlarged scale,

FIG. 5 an end view of one of the chalk marking units of FIG. 1, shown impacting a working surface, taken along line 5--5 of FIG. 1, drawn to the scale of FIGS. 2 and 3, and

FIG. 6 a side elevation view of another embodiment of a chalk marking unit in accordance with the invention, having tapering cowls extending from the outer circumferences of the chalk washer retaining disc to the cord, drawn to the scale of FIG. 2.

FIG. 7 a side elevation view of still another embodiment of the chalk marking unit in accordance with the invention, drawn to the scale of FIG. 2, and

FIG. 8 a perspective view of the chalk line reversible end hook, drawn to substantially full scale.

In the drawings, in which like numbers indicate like elements throughout, FIG. 1 shows an improved chalk line interval marking device 10 according to the present invention. The marking line assembly 11, shown extended for use, is retracted for storage into a canister 12 between uses by a spool, now shown, inside the canister and operated by an exterior retractable crank arm 13.

Line assembly 11 includes a flexible cord 14 and chalk marking units 15 affixed at regular intervals 16 along the cord. An end hook 17 facilitates the placement of line 11 along the surface of a work piece. The marking units 15 are adapted to trap chalk dust particles, whereas cord 14 is selected to remain as far as possible chalk free. When line assembly 11 is snapped toward and against a working surface 18, chalk marks are made only at the points of contact of the outside edges of the units 15. (FIG. 5) Marking units 15 are charged with chalk dust inside canister 12. A felt wiper collar 19 and a split wiper disc 20 of flexible resilient material may be provided to divest units 15 of excess dust as cord 14 is pulled out for use.

Each point-marking unit 15 comprises a thin washer 21 of felt or other chalk dust retaining material, held between a pair of rigid flanges 22 mounted upon a sleeve 23. (FIGS. 2-5) Preferably, flanges 22 and sleeve 23 are of metal, and secured together as by brazes 24. Line 11 preferably comprises a core wire 25 sheathed by smooth flexible plastic 26. Crimps 27 secure sleeve 23 to sheath 26.

Although only the chalk washers 21 are intended to trap chalk dust within canister 12, inadvertent dust deposits may occasionally adhere to other parts of cord assembly 11. For example, the surfaces of the cord 14 may be come soiled in spots with grease or the like, causing the chalk to adhere unwantedly. Or some dust may occasionally be trapped at the junctions between the sleeves 23 and the sheath 26, or in the crimps 27. The present chalk line 10 substantially prevents such deposits from being transferred to the working surface 18 to create confusing extraneous marks. All of line 11 except the edges 28 of marking units 15 is positioned well away from the working surface 18 by the rigid flanges 22. Extraneous dust deposits are unlikely to result in marks well enough defined as to be confusing without actual contact of cord 14 with working surface 18. The edges 28 of the felt washers 21 flatten against the working surface 18 to produce a distinctive rectangular mark. (FIG. 5) To alleviate the tendency of marking units 15 to dredge chalk wastefully from canister 12, cowls 29 are preferably provided. (FIG. 6) The cowls 29 enhance the effectiveness of wiper collar 19 and wiper disc 20. In another embodiment, marking unit 15 comprises a plastic body 30 molded directly upon cord 14. (FIG. 8) Body 30 has tapered ends 31 and a central circumferential groove 32 filled with chalk retaining material.

Line end hook 17, preferably comprises a rigid strip body 31 with a straight center section 32 and perpendicular, oppositely directed end tabs 33 and 34. Hook 17 is normally used as shown in FIG. 8, but may be reversed by rotation about pivot pin 35. See dashed lines, FIG. 8. In this manner, the chalk marking units may be shifted by the length of center section 32.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.